If you are new to the forums, you must register a free account before you can post. The forums have a separate registration from the rest of www.chronofhorse.com, so your log in information for one will not automatically work for the other. Disclaimer: The opinions expressed here are the views of the individual and do not necessarily reflect the views and opinions of The Chronicle of the Horse.

I had two cats just go through this. One was a feral cat that decided to live on my back deck, I noticed he wasn't eating or drinking and then he had some really thick nasty smelling drool. Unfortunately unknown to me at the time my daughter had seen a catnip stuffed toy outside and tossed it in the house for my indoor kitty...and within 48 hours she had the same issues with not eating/drinking and then a thick smelly drool. Took indoor kitty to vet (handling feral kitty can be life threatening) and she was also dehydrated and haad tongue ulcers. I asked the vet about it having never dealt with that before and he said often there's no known reason for how cats get them but they can be catchy.
He gave her fluids and sent her home with 3 bottles of Clavamox liquid so I could also treat the feral cat. Gee thanks for the oral meds for the wild cat doc.
twice a day she got a full dropperful, I found an easy way to give it to her. Wrapped up in a towel kitty burrito style and paid upright on the bed. Grabbed top jaw from above and tips of fingers in sides of her mouth and tilted her head back. Squirted liquid to the back of her mouth. Cleared up the ulcers in 10-14 days. Doc said to just keep giving it to them until ulcers were completely gone.
Did similar for feral cat and Spare kitty was none too hapy about it. But the poor thing was miserable with that festering ulcer on the tip of his tongue (indoor kitty had it in the center of her tongue) and I got maybe a dose a day in him overall....but there were many times we missed days and once in a while I was able to catch him twice a day. His cleared up in 3 weeks.
Vet did say most of the time they clear up on their own but can be dangerous because cats don't eat or drink well when they have tongue ulcers and can end up very sick or pass away from the not eating or drinking enough. Kitty kidneys can't take that.
Hope this helps...I had never dealt with it before either. Haven't forgotten the smell of those ulcers though...poor cats.

You jump in the saddle,
Hold onto the bridle!
Jump in the line!
...Belefonte

Tongue ulcers are a symptom of the calici virus. If that is what it is, he is probably coming home with clavamox. I had a kitten develop tongue ulcers when he was sick with that virus and although he got very sick, he did recover without incident. Jingles for Cisco.

I had one that had ulcers on the inside of his lip. Kinda like a human canker sore. It looked horrible and his lip looked like it was falling off. Turned out it was some kind of allergy and he got weekly Prednisone shots for a month. Also had antibiotics. It cleared right up and when ever it showed signs of returning we hauled kitty in for a shot.

Along with the Clavamox, you can give the cat oral lysine paste. It will help cure the ulcers. I took lysine tablets to cure a ulcerated area on my mouth that didn't respond to the antibiotic cream the dentist prescribed for me.